--- title: Builder summary: A builder type for Logger. url: https://www.fastly.com/documentation/reference/compute/sdks/rust/log_fastly/struct.Builder/ --- **Kind:** Struct **Module:** [log_fastly](https://www.fastly.com/documentation/reference/compute/sdks/rust/log_fastly/) **Package:** log-fastly 0.13.1 **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#353 ```rust pub struct Builder { /* private fields */ } ``` A builder type for [`Logger`](https://www.fastly.com/documentation/reference/compute/sdks/rust/log_fastly/struct.Logger/). You can use this builder to register endpoints, set default endpoints, control the levels of logging messages emitted, and filter messages based on module name. A `Builder` is consumed by calling [`Builder::init()`](https://www.fastly.com/documentation/reference/compute/sdks/rust/log_fastly/struct.Builder/#method-init) or [`Builder::try_init()`](https://www.fastly.com/documentation/reference/compute/sdks/rust/log_fastly/struct.Builder/#method-try_init) to build and automatically initialize the logger, or by calling [`Builder::build()`](https://www.fastly.com/documentation/reference/compute/sdks/rust/log_fastly/struct.Builder/#method-build) to build the logger for manual initialization or nesting within another logger. After you call any of these methods, you can no longer call any of them on that same builder. ## Methods ### build **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#684 ```rust fn build(&mut self) -> Result ``` Build a `Logger`, using up this builder. This is mainly useful if you want to manually initialize the logger, or nest it within another [`log::Log`](https://docs.rs/log/0.4.28/log/trait.Log.html) implementation. This will fail with an `Err` value if: - This builder has already been used to build a `Logger`. - Any of the registered endpoint names are invalid. - Any of the module name filters set by [`Builder::filter_module()`](https://www.fastly.com/documentation/reference/compute/sdks/rust/log_fastly/struct.Builder/#method-filter_module) have invalid [regex syntax](https://docs.rs/regex#syntax). ```rust let logger = log_fastly::Builder::new() .default_endpoint("my_endpoint") .build()?; log::set_boxed_logger(Box::new(logger))?; ``` **Parameters** - `self`: `&mut Self` **Returns** `Result` ### default_endpoint **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#478 ```rust fn default_endpoint(&mut self, endpoint: E) -> &mut Self where E: TryInto, E::Error: Into, ``` Set the default endpoint for all messages. The default endpoint is used when the logging statement does not use the `target: "endpoint"` syntax. This overrides any previous default endpoints, set either by this method or by [`Builder::default_level_endpoint()`](https://www.fastly.com/documentation/reference/compute/sdks/rust/log_fastly/struct.Builder/#method-default_level_endpoint). ```rust log_fastly::Logger::builder() .max_level(log::LevelFilter::Info) .default_level_endpoint("error_only", log::Level::Error) .default_endpoint("my_endpoint") .endpoint("other_endpoint") .init(); log::info!("This will be written to my_endpoint..."); log::error!("...and this will too"); log::warn!(target: "other_endpoint", "This will go to other_endpoint, though"); ``` **Parameters** - `self`: `&mut Self` - `endpoint`: `E` **Returns** `&mut Self` ### default_level_endpoint **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#516 ```rust fn default_level_endpoint(&mut self, endpoint: E, level: Level) -> &mut Self where E: TryInto, E::Error: Into, ``` Set the default endpoint for all messages of the given level. The default endpoint is used when the logging statement does not use the `target: "endpoint"` syntax. This overrides any previous default endpoints set for this level, either by this method or by [`Builder::default_endpoint()`](https://www.fastly.com/documentation/reference/compute/sdks/rust/log_fastly/struct.Builder/#method-default_endpoint). ```rust log_fastly::Logger::builder() .max_level(log::LevelFilter::Info) .default_endpoint("my_endpoint") .default_level_endpoint("error_only", log::Level::Error) .endpoint("other_endpoint") .init(); log::info!("This will be written to my_endpoint..."); log::error!("...but this will be written to error_only"); log::error!(target: "other_endpoint", "This will go to other_endpoint, though"); ``` **Parameters** - `self`: `&mut Self` - `endpoint`: `E` - `level`: `Level` **Returns** `&mut Self` ### echo_stderr **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#607 ```rust fn echo_stderr(&mut self, enabled: bool) -> &mut Self ``` Set whether all log messages should be echoed to `stderr` (`false` by default). If this is set to `true`, all logging statements will write the message to `stderr` in addition to the specified endpoint. This is particularly useful when debugging with [Compute Log Tailing](https://www.fastly.com/blog/introducing-compute-edge-log-tailing-for-better-observability-and-easier-debugging). **Parameters** - `self`: `&mut Self` - `enabled`: `bool` **Returns** `&mut Self` ### echo_stdout **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#595 ```rust fn echo_stdout(&mut self, enabled: bool) -> &mut Self ``` Set whether all log messages should be echoed to `stdout` (`false` by default). If this is set to `true`, all logging statements will write the message to `stdout` in addition to the specified endpoint. This is particularly useful when debugging with [Compute Log Tailing](https://www.fastly.com/blog/introducing-compute-edge-log-tailing-for-better-observability-and-easier-debugging). **Parameters** - `self`: `&mut Self` - `enabled`: `bool` **Returns** `&mut Self` ### endpoint **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#425 ```rust fn endpoint(&mut self, endpoint: E) -> &mut Self where E: TryInto, E::Error: Into, ``` Register an endpoint. ```rust log_fastly::Logger::builder() .max_level(log::LevelFilter::Trace) .endpoint("my_endpoint") .init(); log::info!(target: "my_endpoint", "Hello"); ``` **Parameters** - `self`: `&mut Self` - `endpoint`: `E` **Returns** `&mut Self` ### endpoint_level **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#447 ```rust fn endpoint_level(&mut self, endpoint: E, level: LevelFilter) -> &mut Self where E: TryInto, E::Error: Into, ``` Register an endpoint and set the maximum logging level for its messages. ```rust log_fastly::Logger::builder() .max_level(log::LevelFilter::Trace) .endpoint_level("debug_endpoint", log::LevelFilter::Debug) .init(); log::info!(target: "debug_endpoint", "This will be written to debug_endpoint..."); log::trace!(target: "debug_endpoint", "...but this won't be..."); ``` **Parameters** - `self`: `&mut Self` - `endpoint`: `E` - `level`: `LevelFilter` **Returns** `&mut Self` ### filter_module **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#578 ```rust fn filter_module(&mut self, regex: &str, level: LevelFilter) -> &mut Self ``` Set a logging level for modules whose names match the given [regular expression](https://docs.rs/regex#syntax). By default, logging statements in any module are emitted if their level is within [`Builder::max_level()`](https://www.fastly.com/documentation/reference/compute/sdks/rust/log_fastly/struct.Builder/#method-max_level) and the level for their target endpoint. If you configure filters with this method, the name of the module calling the logging statement must also match one of the patterns, and be within the filter's specified level. ```rust mod my_module { pub fn do_a_thing() { log::warn!("This won't be written, because this module's max level is Error..."); log::error!("...but this will be written"); } } log_fastly::Logger::builder() .max_level(log::LevelFilter::Info) .default_endpoint("my_endpoint") .filter_module("my_module", log::LevelFilter::Error) .init(); log::info!("This won't be written, because it's not in my_module"); // This will only emit one log message, because "my_app$" doesn't match, and // "my_app::my_module" is limited to Error my_module::do_a_thing(); ``` **Parameters** - `self`: `&mut Self` - `regex`: `&str` - `level`: `LevelFilter` **Returns** `&mut Self` ### init **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#624 ```rust fn init(&mut self) ``` Build the logger and initialize it as the global logger. ```rust log_fastly::Builder::new() .default_endpoint("my_endpoint") .init(); log::info!("Hello"); ``` #### Panics This may panic for any of the reasons that [`Builder::try_init()`](https://www.fastly.com/documentation/reference/compute/sdks/rust/log_fastly/struct.Builder/#method-try_init) would return an error. **Parameters** - `self`: `&mut Self` ### max_level **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#545 ```rust fn max_level(&mut self, level: LevelFilter) -> &mut Self ``` Set the maximum logging level for all messages. No messages that exceed this level will be emitted, even if a higher level is set for a specific endpoint or module name. **Note:** The default level is `LevelFilter::Off`, which emits no logging at all. You'll want to change this for most configurations. ```rust log_fastly::Builder::new() .max_level(log::LevelFilter::Warn) .endpoint_level("my_endpoint", log::LevelFilter::Info) .init(); log::warn!(target: "my_endpoint", "This will be written to my_endpoint..."); log::info!(target: "my_endpoint", "...but this won't"); ``` **Parameters** - `self`: `&mut Self` - `level`: `LevelFilter` **Returns** `&mut Self` ### new **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#384 ```rust fn new() -> Self ``` Create a new `Builder`. By default, no endpoints are registered, the maximum log level is set to `Off`, and no module name filtering is done. **Returns** `Self` ### try_init **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#642 ```rust fn try_init(&mut self) -> Result<(), Error> ``` Build the logger and initialize it as the global logger. This will fail with an `Err` value if a global logger is already initialized, or for any of the reasons that [`Builder::build()`](https://www.fastly.com/documentation/reference/compute/sdks/rust/log_fastly/struct.Builder/#method-build) can fail. ```rust log_fastly::Builder::new() .default_endpoint("my_endpoint") .try_init()?; log::info!("Hello"); ``` **Parameters** - `self`: `&mut Self` **Returns** `Result<(), Error>` ## Trait implementations ### impl Debug for Builder #### fmt **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#352 ```rust fn fmt(&self, f: &mut Formatter<'_>) -> Result ``` **Parameters** - `self`: `&Self` - `f`: `&mut $crate::fmt::Formatter` **Returns** `$crate::fmt::Result` ### impl Default for Builder #### default **Source:** https://docs.rs/crate/log-fastly/0.13.1/source/src/lib.rs#374 ```rust fn default() -> Self ``` **Returns** `Self` ## Auto trait implementations - `Freeze` - `RefUnwindSafe` - `Send` - `Sync` - `Unpin` - `UnsafeUnpin` - `UnwindSafe` ## Blanket implementations - `Any` - `Borrow` - `BorrowMut` - `Downcast` - `DowncastSync` - `ErasedDestructor` - `From` - `Into` - `IntoEither` - `Same` - `TryFrom` - `TryInto`